The present invention relates to non-aqueous-based cleaning fluids, methods for cleaning oil-coated substrates, methods for cleaning oil-contaminated drill cuttings, methods for cementing a well casing in a borehole, enhanced oil recovery procedures, methods for lifting oil from a wellbore, and methods for recovering oil from tar sands.
Non-aqueous-based cleaning fluids are used to clean unwanted oil from substrates, e.g., to remove grease spots from clothing or other fabrics. However, these cleaning fluids tend to dilute and spread the oil, as opposed fully removing it from the substrate. Furthermore, many of these non-aqueous-based cleaning fluids are toxic. Accordingly, there is a need for a non-aqueous-based cleaning fluid, and especially a non-toxic fluid, that more fully removes unwanted oil from substrates.
In addition, there is a need for an oil-contaminated drill cuttings cleaning method that is commercially viable and sufficiently efficacious for cleaned drill cuttings to pass a sheen test. Current methods which may clean drill cuttings sufficiently to pass the sheen test in a laboratory environment (e.g., methods using solvents like pentane or carbon tetrachloride) are impractical for commercial use because the solvents can be toxic, very volatile, and explosive. Such limitations require the use of prohibitively expensive equipment to safeguard against the potential hazards arising from the use of such solvents.
Regarding conventional commercial techniques for cleaning drill cuttings, these methods generally either employ a base oil wash (wherein oil-contaminated drill cuttings are contacted with a base oil in an attempt to remove most of the oil contaminant from the drill cuttings) or a detergent wash (wherein oil-contaminated drill cuttings are washed with an aqueous surfactant solution). The base oil and detergent wash processes are typically capable of reducing the oil content on the cleaned drill cuttings to only about 5 to about 20 percent, a level not low enough to pass the sheen test.
Another method for cleaning drill cuttings (hereinafter referred to as UNOCLEAN I) was recently disclosed in U.S. Pat. No. 5,156,686, U.S. Pat. No. 5,213,625, U.S. Pat. No. 5,215,596, and U.S. Pat. No. 5,234,577, each of these patents being incorporated herein in their entireties by reference. While the UNOCLEAN I process can clean drill cuttings sufficiently to pass the sheen test, the UNOCLEAN I process has two drawbacks. First, the apparatus employed in the conventional commercial base oil and detergent wash processes must be modified in order to adapt them for use in the UNOCLEAN I process. Second, although the carboxylic acid used in the UNOCLEAN I process is non-toxic, the carboxylic acid must be recycled due to its high cost. The recycling step requires the use of an acid (e.g., HCl) and a base (e.g., NaOH).
There is also a need for a method for cementing casings in wellbores drilled, at least in part, with an oil-based drilling fluid.. The current cementing methods tend to leave oil on the wellbore and/or casing surfaces, frequently necessitating the need for expensive, remedial cement squeeze procedures.
Likewise, a demand exists for improved enhanced oil recovery techniques as well as better methods for lifting viscous oils from oil wells.
Furthermore, while commercial technologies exist for extracting oil from water-wet tar sands, there is no commercial technology for removing oil from oil-wet tar sands.